| 1 | EFFECT OF SILICON ON THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF YTTRIUM MODIFIED Ni_3Al BASE ALLOY IC6显示文摘The effect of different amounts of silicon on the microstructure of the yttrium modified Ni3Al base alloy IC6 was studied with transmission electron microscope (TEM). The chemical compositions of phases formed due to the presence of silicon and yttrium were analyzed with energy dispersive spectrum(EDS) technique of electron probe microstructural analysis (EPMA). The results showed that a bulk shape phase rich in Mo and Si was formed in the alloys with addition of 0.10-0.20wt%Si and 0.12wt%Y, and that a needle like phase named Y-NiMo was precipitated in the interdendritic area in the alloy with addition of 0.30wt%Si and 0.12wt%Y besides the formation of the bulk shape phase mentioned above. The stress rupture properties under 1100℃/80MPa and the thermal fatigue properties at 1100℃ were improved by adding 0. 12wt%Y but decreased by adding 0.10-0.30wt%Si and 0.12wt%Y. The addition of 0. 10-0.20wt%Si and 0.12wt%Y has no obvious influence on the tensile properties of alloy IC6 at room temperature (R. T.), 760, and 900℃, respectively. | C.B.Xiao Y.F.Han X.A.Zhang | 1998 | Acta Metallurgica Sinica(English Letters)1998，11，6： | 1 |
| 2 | ON FATIGUE CRACK PATH DEVIATION AT ELEVATED TEMPERATURE IN ELECTRON BEAM REPAIRED WELDMENTS OF TURBINE DISK显示文摘Fatigue crack growth behaviors in electron beam weldments of a nickel-base superalloy are studied. The objective of this paper is to discuss effects of the inhomogeneity of mechanical performance on fatigue crack growth (FCG) rate and crack path deviation (CPD). The base metal served in a turbine disk of aerospace engine was selected to fabricate bead-on-plate weldments by using electron beam welding. Some wedge-type opening loading specimens, notched in three different zone of weld metal, HAZ and base metal, were employed and performed fatigue crack growth tests at 650℃. The results show that the fatigue crack growth of electron beam welded joints is instable due to the influence of mechanical heterogeneities. Owing to the crack deviation at the weld metal and hcat-affected-zone (HAZ), the effective growth driving force at the tip of fatigue crack was reduced with the reduction of the effective stress intensity factor (SIF) which finally causes fatigue crack rate decrease. Fatigue crack was strongly affected by size and the symmetrical characteristics of the plastic zone at the crack tip, which means that the integrity of the welded structure containing the fatigue crack mainly depended on the toughness of the low strength zone. | H.Q.Zhang H.Y.Zhao Y.H.Zhang L.H.Li X.A.Zhang | 2004 | Acta Metallurgica Sinica(English Letters)2004，17，4： | 0 |
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